An Analysis of Phase Transformations for Porous Shape Memory Alloy Considering Hydrostatic Stress

Abstract

According to micromechanics, consider the porous shape memory alloy (SMA) as a composite-sphere model. Isolate a constant thickness spherical shell which is composed of SMA, and is traction free on its inner surface and subjected to the uniform hydrostatic pressure and the deviatoric stress on its external surface. Then, a constitutive model for porous SMA considering hydrostatic stress is proposed by elasticity solution. The stress distribution of the spherical shell was calculated. Corresponding to different applied stresses, the spherical shell is divided into different regions of pure austenite, pure martenite, and austenite/martensite mixture under isothermal circumstances. The martensite volume fraction is then obtained. The predicted results have been compared with the obtained experimental data by Zhao and Sia Nemat-Nasser. It shows that the modeling results are in good agreement with the experiments and the initial phase transition point for porous SMA is lower than the dense SMA.

Computational Models for Functionally Graded Composites Using the SMA as the Metallic Phase

“…Distinctive properties of SMAs are a consequence of their ability in changing their crystallographic structure between a high symmetry parent phase (austenite) and a low symmetry phase (martensite) in response to mechanical and/or thermal loads. For a comprehensive discussion on general properties of SMAs and the phase transformation phenomenon, readers are referred to Boyd and Lagoudas [2], Lagoudas et al [3] and Liu et al [4,5].…”